This invention pertains to electro-mechanical switching systems.
Stereophonic sound, the sound accompanying motion pictures, monaural sound, and possibly other acoustic information is now frequently made available to persons on an individual basis. This mode is widespread on transport aircraft.
It has been found as a practical matter that the electrical energizing system for such purposes is typically in operation on almost a 24 hour per day basis. If program material is not supplied, then a 1 to 6,000 hertz square-wave test signal is frequently maintained; thereby to enable a ready check to determine whether or not the few hundred seats in the vehicle have an operative electro-acoustic system.
Because of the steep wavefronts of the square waveform, this signal is known to cause failure of the electrical to sound transducers long before normal use would cause failure. Also, normal use tends toward failure, and any means that removes the transducers from operation other than when useful operation is required to provide sound to a passenger, has been calculated to extend the life of a transducer about 800%.
Locating a pair of small transducers in the arm rest of a seat in an airplane is known. Also, the use of an acoustic plug therein that prevents sound from being emitted except when a hollow acoustic connector, usually a pair for stereo sound, is inserted into the enclosure containing the transducers is known. Further, an electrical bridging contact in the acoustic connector has been proposed for distribution to passengers who pay to hear certain sound programs, such as that pertaining to a motion picture.
Another arrangement has been proposed in which two transducers are contained within the known housing having an insertable acoustic-use element and a switch is included within the housing. The configuration is adapted to allow selective operation of the transducers with respect to two or more sources of signal. An open circuit occurs when a transducer is not energized. The structure of the switch shown is atypical to a preferred arrangement for these elements.
Another arrangement is known that has the nature of an acoustic manifold. One transducer has a chamber into which a plurality of stethoscope-like listener devices may be selectively plugged. The acoustic orifices are sealed when a listener device is not plugged in.